The present invention relates to a valve for controlling a fluid flow and more particularly to a valve with an integral piezo-electric actuator arranged to control the operation of the valve.
Valves and spool valves are well known for controlling fluid flow, and many different designs and arrangements are well known in the art. Furthermore, electrically controlled valves are also known controlled by a solenoid to directly open or close the fluid path, or to control a diaphragm or iris to block the valve bore. However, even with such solenoid valves, there is still a further need for a valve which can be easily constructed and readily controlled by an electrical control circuit.
It is an object of the present invention to integrate a piezo-electric actuator into a valve to provide a readily electrically controllable valve for the control of a fluid flow.
In order to meet the above object, according to the present invention there is provided an electrically controllable valve comprising at least one input port and one or more output ports, at least one sealing means being arranged to control the flow of a fluid between said input port and at least one of said output ports, said valve being characterised by further comprising one or more piezo-electric actuators arranged to control the state of said sealing means, whereby the flow of fluid through said valve may be electrically controlled.
In a first embodiment, the valve may further comprise a valve rod arranged to move within a bore, the valve rod having a first and a second sealing member disposed at respective fixed positions thereon such that in one position the sealing members cause fluid to flow from the input port to the first output port, and in a second position the sealing members cause the fluid to flow from the input port to a second output port. In addition, a spring means arranged to bias the valve rod into the first position may also be provided, and a pilot hole arranged to vent fluid from within the hole to the opposite side of one of the sealing members is also provided and arranged to be opened or closed by means of the piezo-electric actuator. When the pilot hole is open, fluid is free to flow from within the bore to the opposite side of one of the sealing members thereby forcing the valve rod into the second position. In this way, the piezo-electric actuator may control the position of the valve rod and hence the state of the valve.
Furthermore, in the above first embodiment, the valve may further include a pilot channel arranged between one end of the bore and the pilot hole through which the fluid may flow when said pilot hole is open, the pilot channel being further provided with an exhaust port arranged to be closed when the pilot hole is opened and vice versa. The exhaust port may be closed by operation of the first piezo-electric actuator, or by operation of a second piezo-electric actuator.
Alternatively to the above, in a second embodiment of the present invention the valve may further comprise a slidable sheet provided with a hole extending from one side to the other, the sheet being arranged transverse to a bore having the inlet port at one end and the outlet port at the other, and being further arranged to slide in the transverse plane in response to actuation of the piezo-electric actuator. This operation may control the valve such that in a first mode of operation the sheet is held such that the hole is not within the bore whereby the valve is then deemed closed, and in a second mode of operation the sheet is moved such that the hole is within the bore whereby the valve is then open, and fluid may flow from the input port to the output port.
In this second embodiment, a second piezo-electric actuator may also be provided arranged to complement the action of the first piezo actuator so that, for example, the first piezo actuator is arranged to push the sheet along the transverse plane, while the second piezo actuator pulls the sheet, and vice versa. The sheet is preferably made of a substantially friction-less material such as, for example, polytetrafluoroethene.
In either of the above-described arrangements, the fluid is preferably a pressurised gas.